Southland Stags' player Hoani MacDonald is reported to be in a critical but stable condition after suffering cardiac arrest mid-match during the NPC Championship semifinal against Counties-Manukau in Pukekohe on Saturday afternoon.

MacDonald had vigorous CPR performed on him by paramedics before being taken away in an ambulance to Middlemore Hospital ambulance at 3.15pm.

"Macdonald was taken by ambulance from ECOLight Stadium to Middlemore Hospital," a New Zealand Rugby Union statement said.

"He has been put in an induced coma and is stable."

A spectator said she saw MacDonald collapse away from the play before he was put in recovery position by a team mate.

"He tried to stand up but then just fell over holding his chest," Charleen Beach said. She watched as medics performed CPR for nearly 10 minutes before a defibrillator was used.

A stadium staff member on site said "we got him back".

Counties Manukau won the match 48-23 with four tries in the final 11 minutes, earning a home match for the NPC Championship final against Otago.

They initially kept playing while MacDonald was down, with Southland even scoring a try.

MacDonald made his New Zealand Maori debut in 2004. He has also represented the Junior All Blacks (in 2006 and 2007).

At provincial level he plays for Southland and the Highlanders in Super Rugby.

He hails from the MacDonald family of Marlborough, one of the most noted rugby families in the country.